Transporting fluids at sub-micron length scales is becoming increasingly important in a wide range of applications. For example, study of the transport of liquids through carbon nanopipettes has increased due to interest in understanding the motion of highly confined fluids and the prospect of building nanofluidic devices from nanopipes in the future. The flow of liquids through carbon pipes of sub-micron diameter has been studied by Miller et al, 2001 J. Am. Chem. Soc. 123 12335, which describes electro-osmotic flow in carbon-pipe-based membranes formed in the pores of perforated alumina membranes. A Coulter counter has been produced by Sun et al, 2000 J. Am. Chem. Soc. 122 12340, and Ito et al, 2003 Anal. Chem. 75 2399, which describe embedding individual carbon pipes with diameters of a few hundred nanometers in an epoxy layer. Nanoassembly and microfabrication techniques have been applied to produce nanofluidic devices in Bau et al, 2004 Nanofabrication: Technologies, Devices, and Applications (Proc. SPIE vol 5592) ed. W Y-C Lai, S Pau and O D Lopez (Philadelphia, Pa.,: SPIE) 201-13 (Invited Paper). Gogotsi et al, 2001 Appl. Phys. Lett. 79 1021, has used a transmission electron microscope to study the behavior of thermally actuated liquids that are confined in hydrothermally synthesized carbon nanotubes. Rossi et al, 2004 Nano Lett. 4 989, describes the use of a scanning electron microscope to study the wetting properties of carbon tubes with diameters of 50 to 300 nanometers grown in alumina pores. Optical microscopes have been used to study capillary filling, condensation, and evaporation of liquids in Kim et al, 2004 Nano Lett. 4 2203, and the filling of particles into sub-micron, alumina-grown nanotubes has been studied with a fluorescence microscope in Kim et al, 2005 Nano Lett. 5 873.
The production of nano- and micro-sized structures typically requires a difficult, and often unattainable, assemblage of multiple components. Existing technology cannot readily probe biological cells and organelles or provide for fluid and macromolecule transfer in the nano-scale. A typical method of producing a carbon-fiber electrode, for example, requires the difficult task of inserting a carbon fiber into an electrode glass tube and affixing it to a single strand conductor using conducting silver paint. FIG. 1 is an example of this process. The end of the glass is typically sealed around the carbon fiber by using a heating coil as shown in FIG. 2. Producing devices through these type of manual processes is painstaking and not applicable to mass production. Methods to fabricate probes on the nano- and micro-scale have been desired in the art. Accordingly, there remains the need to provide a variety of devices at the nano- and micro-scales using processes that are efficient and commercially amenable to scale-up.